The constituency is centred on the town of Lewes, for which it is named. However, the constituency also covers most of the Lewes district and parts of the Wealden district which are rural and semi-rural and all in outer parts of the London Commuter Belt, though with a high number of people who have retired from across the country.[2]

The constituency of Lewes has existed since commoners were first summoned to Parliament in 1295, the Model Parliament. This is the county town, though less significant in population today, far surpassed by the City of Brighton and Hove — it has nonetheless been continuously represented since that date.

Between 1874 and 1997, the constituency's electorate in the elections sent only ConservativeMPs.